True breast development in both females (thelarche) and males (gynecomastia)
is due to growth of glandular tissue, not fat. For adolescents who appear
to be developing breast tissue, it is important to differentiate between
glandular tissue (firmer and somewhat tender tissue immediately under
the areola) and fat (increase in fat in the breast tissue, along with
fat in other sites of the body). Some overweight adolescents may not be
developing sexually, but merely increasing the amount of fat in their
breast tissue. If a pre-pubertal girl or boy is already overweight, she/he
can be expected to gain weight even more rapidly when she/he eventually
does go through puberty.

Weight

Between 8 and 14
years of age, girls tend to gain weight more rapidly than boys, but the
50th percentile BMI-for-age measures for girls and boys are nearly identical.
A girl at the 50th percentile gains four times as much weight between
10 and 14 years of age as she does between 16 and 20 years of age (40
pounds, compared to 10 pounds). After 14 years of age, weight continues
to increase, but at a decreased rate. Because boys have their growth spurt
about two years later than girls, the maximum rate of weight gain for
boys is between 12 and 16 years of age. A boy at the 50th percentile in
weight-for-age gains about 45 pounds over those four years, while he gains
an additional 20 pounds between 16 and 20 years of age.

Stature

Until 10 years of
age, boys and girls grow in stature at nearly identical rates. Around
10 years of age, girls at the 50th percentile begin to grow taller more
rapidly than boys. The growth rate for girls continues to be greater than
boys between 10 and 13 years of age. After 13 years of age, the height
spurt of girls generally is completed and the boys' height spurt is in
its early phase. Therefore, by 14 years of age boys are taller than girls,
on average. Girls generally gain no more than 2 inches in stature after
the onset of menstrual periods. However, males can continue to grow in
stature in their early twenties. By the time that adult stature is reached,
the 50th percentile for stature-for-age is about 6 inches higher for males
than for females. Thus, the average adult male is about 70 inches tall,
and the average adult female is about 64 inches tall.